sixel: purge images at current cursor row

When printing a character, or starting a new sixel image, purge all
images that cover the cursor's current row.

sixel.c

@@ -39,6 +39,8 @@ sixel_init(struct terminal *term)
 
     count = 0;
 
+    sixel_purge_at_cursor(term);
+
     /* TODO: default palette */
 }
 
@@ -52,6 +54,22 @@ sixel_destroy(struct sixel *sixel)
     sixel->data = NULL;
 }
 
+void
+sixel_purge_at_cursor(struct terminal *term)
+{
+    const int row = term->grid->offset + term->cursor.point.row;
+
+    tll_foreach(term->sixel_images, it) {
+        const int start = it->item.pos.row;
+        const int end = start + it->item.rows;
+
+        if (row >= start && row < end) {
+            sixel_destroy(&it->item);
+            tll_remove(term->sixel_images, it);
+        }
+    }
+}
+
 void
 sixel_unhook(struct terminal *term)
 {
@@ -74,13 +92,6 @@ sixel_unhook(struct terminal *term)
         term->sixel.image.data,
         term->sixel.image.width * sizeof(uint32_t));
 
-    tll_foreach(term->sixel_images, it) {
-        if (it->item.pos.row == image.pos.row) {
-            sixel_destroy(&it->item);
-            tll_remove(term->sixel_images, it);
-        }
-    }
-
     tll_push_back(term->sixel_images, image);
 
     term->sixel.image.data = NULL;

sixel.h

@@ -9,6 +9,7 @@ void sixel_put(struct terminal *term, uint8_t c);
 void sixel_unhook(struct terminal *term);
 
 void sixel_destroy(struct sixel *sixel);
+void sixel_purge_at_cursor(struct terminal *term);
 
 void sixel_colors_report_current(struct terminal *term);
 void sixel_colors_reset(struct terminal *term);

terminal.c

@@ -2128,6 +2128,8 @@ term_print(struct terminal *term, wchar_t wc, int width)
     print_linewrap(term);
     print_insert(term, width);
 
+    sixel_purge_at_cursor(term);
+
     /* *Must* get current cell *after* linewrap+insert */
     struct row *row = term->grid->cur_row;
     struct cell *cell = &row->cells[term->cursor.point.col];